273 4bbl, carb replacement?

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Exjouster

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Hey all, looking for some advice! I have a 67 Dart GT running a 273 with an Edelbrock 1404 500 cfm. (Not sure on cam or engine internals, as modification from a 2bbl was done by a previous owner.) Car is running kinda hot (mainly when stopped in traffic), stalls sometimes on acceleration from a stop, and seems overall anemic in performance. Mechanic said the carb may be bad, and engine overall is a bit "tired" (car had sat non-running for almost 5 years before I got it.)

Has had new water pump, radiator, thermostat, 6 blade steel fan put in, shroud, and system flushed...all that helped, but still running a bit warm.

So, does this sound like a carb replacement issue? (Looking at about $350 to get a new 1404.) And if so, should I go with another 1404, or something else? If a 1404, should I go with a manual or vacuum choke, and mechanical or vacuum secondaries?

Also, any other advice for getting some more power out of it on a shoestring budget? Running gear is a 904 auto, new 3.55 gears.
 
That's the same build as my 66 Barracuda. What ignition are you running? What's your timing set at? You could gain some help on acceleration by increasing your timing. If it isn't advanced enough it could also run hot. I run a Pertronix Igniter II and my initial timing is set about 16*, with total timing at 36*. A rebuilt distributor also helped my idle.

When you say kinda hot in traffic, is that 200* or higher? Do you have a fan shroud?
It helps to have a hood to radiator seal and a hood to cowl seal for proper air flow.

'course it could still use a carb rebuild since it sat so long. I run a 1404 on mine and it's peppy and pulls good, especially at 3500 rpm and above!!
 
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66fyssh said:
That's the same build as my 66 Barracuda. What ignition are you running? What's your timing set at? You could gain some help on acceleration by increasing your timing. If it isn't advanced enough it could also run hot. I run a Pertronix Igniter II and my initial timing is set about 16*, with total timing at 36*. A rebuilt distributor also helped my idle.

When you say kinda hot in traffic, is that 200* or higher? Do you have a fan shroud?
It helps to have a hood to radiator seal and a hood to cowl seal for proper air flow.

'course it could still use a carb rebuild since it sat so long. I run a 1404 on mine and it's peppy and pulls good, especially at 3500 rpm and above!!
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Running an electronic ignition, not sure what brand. Have a new hood to radiator seal in place, but gotta find a hood to cowl seal for it. Fan shroud is in place.

By kinda hot, it’ll spike up to about 210 if I am stopped in traffic for long periods, but comes right back down once I’m moving. I did bump the idle up a bit to keep the fan moving more air.

Not sure where the timing is at...gotta go but a light and remember how to time it! Used to know 30 years ago, but time has taken its toll on the old brainpan!!

Now it looks to me like it’s a mechanical secondary, or am I wrong on that?
 
As long as it's not blowing coolant out I wouldn't be too concerned. You may need a new radiator cap. It could be loosing pressure thus lowering the boiling point. What is your timing set at. 273's like 10-15° initial. Not enough advance can aggrevate overheating. Too much can cause detonation. That carb should be perfect and it might need to be freshened up but I doubt it's the cause of your heating issue. A good cooling system flush may help.
 
I’m running into the same problem on my 65 Dart 273 on running alittle warm in traffic above 200 I’m running factory fan and shroud. I bought a new radiator as mine is original and little crusty. Check your timing also mine was at factory and I changed mine to what the guys here suggest 10-15 initial, engine runs way better even drivable when cold. I’ll keep you posted if new aluminum radiator helps my issue. Dustin
 
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I'd put a carb kit in the carb you have, but first check to see if the secondaries are fully open when the pedal is on the floor.
If you only have cooling problems at idle, you are not pulling enough air. I'd recommend a factory flex fan and be done. My 273 runs fine, no shroud, but with a 3 core radiator.
I'd run champion N-10Y same as a Commando engine. Low compression 340's run the same plug as the high compression 340's. Set timing at 10 degrees to start.
 
66fs said:
I'd put a carb kit in the carb you have, but first check to see if the secondaries are fully open when the pedal is on the floor.
If you only have cooling problems at idle, you are not pulling enough air. I'd recommend a factory flex fan and be done. My 273 runs fine, no shroud, but with a 3 core radiator.
I'd run champion N-10Y same as a Commando engine. Low compression 340's run the same plug as the high compression 340's. Set timing at 10 degrees to start.
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Stock engine, stock heat range plugs. HP273's run n9y's and the 2 barrel engines run 14's. If you rebuild and your compression is somewhere in between then run a plug between the two.
I bet your 3 core radiator helps a bunch. Mopar undersized their radiators from what I see. There's not much room to grow with the stock radiator. I still have the stock radiator in my 66 Dart. It is a factory HD/AC radiator though. With a 4 blade fan, no issues.
 
4spdragtop said:
Did you verify new thermostat before installing?
Similar issues with my 273. Turned out to be thermostat.
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Make sure you test your new thermostat in a pan of water on the stove with a thermometer. I have had a rash of bad thermostats right out of the box. They were NAPA's though. I'm loosing faith in their quality. LOL
 
toolmanmike said:
Stock engine, stock heat range plugs. HP273's run n9y's and the 2 barrel engines run 14's. If you rebuild and your compression is somewhere in between then run a plug between the two...
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All 273 4 barrel engines were N10Y. 68 to 72 340's were N9Y with 73 340's N12Y. The plug range has more to do with performance level than compression. I run platinum plugs now, as I feel they last longer and have a wider heat range.
 
I would before spending a dime play with the timing (advance it) until it pings
slightly under hard acceleration. Once you find this spot then retard it slightly and test it again for no ping. Then get a timing light check where the timing is for mechanical and vacuum limits. Is your 273 an original 2 barrel or 4? This will determine the
compression and what octane gas it will need. Retarded timing causes symptoms you
discribe.
 
66fs said:
All 273 4 barrel engines were N10Y. 68 to 72 340's were N9Y with 73 340's N12Y. The plug range has more to do with performance level than compression. I run platinum plugs now, as I feel they last longer and have a wider heat range.
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Sorry but N9Y's for the 4 barrel engines. Photo is out of my 66 factory service manual. (and we aren't talking about 340's here)

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66jim said:
I would before spending a dime play with the timing (advance it) until it pings
slightly under hard acceleration. Once you find this spot then retard it slightly and test it again for no ping. Then get a timing light check where the timing is for mechanical and vacuum limits. Is your 273 an original 2 barrel or 4? This will determine the
compression and what octane gas it will need. Retarded timing causes symptoms you
discribe.
Click to expand...
Car was originally a 2 bbl
 
Exjouster said:
Car was originally a 2 bbl
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If you don't croud the timing too much you should be able to burn regular or maybe e10. I have run E10 in my 318-2barrel but it runs much better with non-ethanol regular if it's available in your area.
 
Exjouster said:
Car was originally a 2 bbl
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Go for 87 octane, should be about 8.5 compression tune from there. With 8.5 any gas above 87 octane is just a waste of money.
Look into a cold air intake (Florida!) and maybe plugs one heat range cooler and
Electric fan(s) these are "free" power.
 
Good Robertshaw AWOL
not to sweat 210
but check everything
timing too advanced or retarded
vac canister and hooked to correct port
check for lean
cold air good suggestion
check out Champion LY plugs RFN12LY on low compression motor (take less timing)
radiator flushed?
how many blade fan and fan clutch?
what's the pitch on your fan?
if everything else is ok add a pusher fan
but do not use it as a band aid for poor tune or mechanicals
It will also make your AC work better in stop and go
 
toolmanmike said:
Sorry but N9Y's for the 4 barrel engines. Photo is out of my 66 factory service manual. (and we aren't talking about 340's here).
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Hah, I should have been careful in doubting you. The 66 FSM would trump the 68 Motors Manual in my mind. Do you have a 72 or 73 FSM? Now I'm curious what plugs they specify for the low compression 340's.
 
Garrett Ellison said:
Okay, I'm Game! What do you need to avoid when you swap over to a four barrel?
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Too big a cam mostly. I ran a high compression 273 4 speed, while my brother ran a 2 barrel 273 Auto converted to 4 barrel. He ran the stock Commando cam, while I went bigger. His car was quick, would cruise at 100 mph all day long and had a top end of 140 mph. In their best configuration, they were both running small TQ carbs. At one point near the end of daily driver status, he had me swap to open chambered 675 heads so he could run regular gas.
 
champion 12 or 14 for late smog motors
but the LY series works best to eliminate the idling (and smog)( and missing) problems for these motors
carbs/ MAKE IT WORK
what you have
AVSII
TQ
small primaries and big secondaries
do not worry about an AVSII or TQ being "too big"
the Air door limits the size
 
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